The present invention relates generally to surface ice detection systems, and, more particularly, to ice detectors for use in aircraft.
The problems relating to the formation of ice on aircraft are well known, and date from the early days of aviation. In certain climatic conditions, ice has a tendency to form, especially in the vicinity of the leading edges of airfoil surfaces, in sheets of substantial thickness. The ice not only increases the effective weight of the aircraft, but it can also increase drag resistance and reduce the lift provided by the airfoil.
Various techniques have been employed in the past for the detection of ice, but have all proved unreliable for one reason or another. One prior art method of ice detection is known as the orifice or pressure-probe method, and utilizes forward facing orifices, the formation of ice on the orifices being detected as a decrease in pressure. Other ice detection techniques depend on the detection of a variation in a particular mechanical or electrical parameter, such as electrical or heat conductivity, or the attenuation of light passed through the ice. While some of these techniques may operate reasonably satisfactorily on fixed-wing aircraft, there are additional problems posed by the detection of ice on helicopters. Typically helicopters are used at lower altitudes, and are more likely to encounter icing conditions than modern fixed-wing aircraft. Moreover, many of the prior art techniques are incapable of being adapted for use on rotating surfaces. Consequently, no completely satisfactory method has heretofore been available for the detection of ice on helicopter rotor blades.
It will be apparent from the foregoing that there exists a clear need for an ice detection system which can reliably indicate the presence of ice on aircraft, and particularly on rotor blades of helicopters. The present invention fulfills this need.